Electron discharge device employing cavity resonators



. ct. 26, 1948. L. s. NERGAARD 9 9 ELECTRON mscmmsm DEVICE EMPLOYING 0mm: RESONATORS Filed Dec. 14; 1'94;

Srmentor Patented Oct. 26, 1948 ELECTRON DISCHARGE DEVICE EMPLOYING CAVITY RESONATORS Leon S. Nergaard, Princeton, N. .lL, assignor to Radio Corporation of America, a corporation of Delaware Application December 14, 1943, Serial No. 514,206

8 Claims.

My invention relates to electron discharge devices and circuits therefor and particularly to such devices and circuits useful at ultra high frequencies.

Electron discharge devices using cavity resonators are used at ultra high frequencies. In the triode type, the electrodes are usually arranged in the order of cathode, grid and anode, and may have radially directed supports and lead-ins extending through the envelope and contacting the cavity resonator circuits. For example, in the triode an input cavity resonator, which may be of the coaxial line type, is connected between the cathode and grid, and the output resonator is connected between the grid and anode. other type of tube referred to as an inductive output tube, the electrodes are in the order of cathode, grid, accelerator and collector. The input resonator, usually of the coaxial line type, is connected between the cathode and grid, a second resonator is connected between the grid and accelerator, and the output resonator is positioned between the accelerator and collector. The resonator connected between the control grid and acu celerator or screen is used to bring the accelerator to cathode potential for radio frequencies and is used for regeneration to compensate for the diode loading.

At ultra high frequency it is desirable to so construct and arrange the leads to tube electrodes that they have as low inductance as possible, or, alternatively, to so arrange them that they comprise conductors of transmission lines which may be joined with an external circuit, Leads of triodes and of the triode section of inductive output tubes have been brought out in thesame space sequence as the electrodes have within the tube, namely the sequence cathode, grid and anode, or in the case of the inductive output tube, the accelerator and collector. Because of this arrangement it is necessary to use the so-called grounded grid circuit, which is characterized by having a circuit between the grid and plate, or grid and accelerator. The disadvantages of this arrangement are, first, the full diode loading of the tube appears across the input circuit. This requires a higher driving power and results in a lower power gain. Second, in the inductive output tube the circuit between the grid and accelerator is used to bring the accelerator to cathode potential as far as radio frequency is concerned, or to introduce regeneration to compensate for the diode loading. Because regeneration tends to be unstable, tuning of the circuit is critical. It is'desirable to eliminate diode loading and to remove In anthe circuit between grid and accelerator. This would simplify tuning of the tube circuit without sacrificing performance.

It is, therefore, the principal object of my invention to provide an improved form of an electron discharge device and circuit useful at ultra high frequencies.

' It is another object of my invention to provide such a device utilizing cavity resonators but in which the usual diode loading associated with tubes of this type is eliminated, and in which circuits requiring critical tuning are made unnecessary.

It is a further object of my invention to provide such a device utilizing cavity resonator circuits in which the grounded grid circuit is avoided.

The novel features which I believe to be characteristic of my invention are set forth with particularity in the appended claims, but the invention itself will best be understood by reference to the following description taken in connection with the accompanying drawing in which Figure 1 is a longitudinal section of an electron discharge device and its associated circuit made according to my invention, Figure 2 is an end view of the cathode of the device shown in Figure 1, Figure 3 is an end View of the cathode and grid of the device shown in Figure 1, and Figure 4 is a diagram showing an equivalent circuit of the device shown in Figure 1.

To overcome the objections above to the usual lead arrangement, I have devised a structure in which the usual lead sequence is changed to the sequence grid, cathode, anode 0r accelerator, thus permitting the use of grounded cathode circuits. An example of such a device and circuit is shown in Figure 1,

Referring to Figure 1 I show an elongated evacuated envelope I 0 containin at one end an indirectly heated cathode l I followed by grid l2 and accelerator IS, a second accelerator M and a collector It provided with cooling fins l6 and secondary electron emission suppressor ring ll, the

collector being supported by leads l5 and the suppressor by lead ll. The suppressor is maintained during operation of the device at a lower potential than the collector.

The indirectly heated cathode ll is provided with a shielding andfocusing collar [8 from which I3 andthe cathode H in position Within the en- 3 velope. The cathode is also provided with a plurality of leads, such as 20, which extend through the base of the envelope of the tube, one of the leads 2| serving as a heater lead for the cathode, the other side of the cathode heater being connected through the support wires ll, collar l8 and support 19 to the outside of the envelope. The lead2l is so placed that interaction between it and the fields within the resonator are reduced to a minimum.

The grid as shown in Figures 1 and 3 comprises a ring-shaped member l2 supporting a plurality of transverse wires or mesh. This grid has support wires 22 extending through the space between the cathode ii and the collar l8 and through the press of the envelope. Thus the grid and cathode leads cross each other.

The accelerator I3 is supported by a ringshaped lead-in and. support member l3 also sealed through the envelope of the tube.

It will, thereforebe seen that-the leads for :the electrodes are now in the orderof grid leads 22, cathode lead l9 and accelerator lead l3.

The input-circuit comprises a coaxial line type resonator comprising an inner tubular member 125 .and outer tubular member 26 and closed at the outer end by means of the disc-27. The inner tubular member 25 is capacitively coupled to the grid leads22 by means of the collar 22' fixed ;to and connected to the grid leads and insulated from the inner tubular member by the insulating collar 28, preferably of mica. The other end of the input resonator circuit is connected to the cathode lead l9 by means of resilient spring type .fingersdil secured to a radially extending wall 29 at the inner end of the resonator. The input signal is provided by means of the coupling loop3l.

The output resonator 32 is positioned between the accelerator l3 and accelerator l4 and functions in a manner now well known, as described in Haefi Patent 2,237,878. The accelerator or screen electrode i3 is connectedtoa: tubular member '34 of the resonator x32 through the spring clip fingers 34 and capacitively coupled .to thecathode by flange 34" insulated from the end wall member 29 by the insulating ring 35, preferably of mica. The other tubular member 33. shields a space between the gap 32 in the resonator 32 and the second accelerator I4. The

output may beitaken from the outputresonator by means of the coupling loop 36.

' The press supporting the collector l may be protectedby overlapping shields 31 supported from the press by means of the support wires 38, and each covering about 120.

It will thus be seen that in a devicemade according to my. invention the order. of the electrode leads is changed and due to the arrangement shown the accelerating electrode may-be capacitively coupled directly to the cathode to bring it to ground radio frequency potential, thus making it unnecessaryto provide the auxiliary resonator.

While in the arrangement shown a .small amount of couplingexists between the grid cathode circuit and the accelerator-cathode circuit, because of the inductance of the length of the grid support which extends beyond the cathode, the

design providedis suchthat this coupling is practically negligible. The tube and .circuit .shown are for an amplifier buthas two instead of the usual three tuned circuits. This is possible because the cathode and the acceleratorl3 are; brought to the same R-F. potential by flange 34" and the wall 29 with the intermediate insulating member 35.

Because the focusing cylinder I 8 encloses both the grid and cathode and is held at cathode potential it serves to focus the electron beam through the tube. This arrangement has the advantage that the focusing electrode is held at fixed voltage instead of the varying voltage of the usual inductive output tube.

In Figure 4 is shown the equivalent circuit, the same numerals indicating the same elements as in the other figures.

While I have indicated the preferred embodiments of my invention of which I am now aware and have also indicated only one specific application for which my invention may be employed, it will be apparent that my invention is by no means limited to the exact forms illustrated or the use indicated, but that many variations may be made in the particular structure used and the purpose for which it is employed without departing from the scope of my invention as set forth in the appended claims.

What I claim as new is: 1

1. .An electron discharge device having a cathode electrode, grid electrode and another electrode aligned in the order named, said cathode electrode having lead and support conductors, said grid electrode having lead and support conductors extending across but out of contact with the cathode conductors, a cavity resonator coupled between the grid conductors and cathode conductors on the opposite side. of the crossedover portions from said grid electrode and cathode electrode.

2. An electron discharge device having an elongatedenvelope containing a cathode electrode, grid electrode and another electrode arranged alongthe longitudinal axis of said envelope in the order named, said cathode electrode having radially extending lead-in and supporting conductors, said grid electrode having lead-in and supporting conductors extending across but out of contact with the cathode conductors within said envelope and extending through said envelope, and a cavity resonator coupled between the grid conductors andthe cathode conductors on the outside of said onvelope.

3..An electron discharge device having an envelope and containing in the order named a cathode electrode, grid electrode, accelerator electrode and collector electrode, said cathode electrode being provided with radiallyextending conducting supporting means extending through the wall of the envelope, said grid electrode being supported on leads extending through but out of contact with said cathode electrode supporting means and through said envelope, said accelerator electrode being provided with conducting supporting means extending radially through the wall of the envelope of said tube, a cavity resonator coupled between the cathode electrode supporting means and said grid leads on the outside of said envelope, and a capacity coupling between said accelerator electrode and said cathode electrode.

4. An electron .discharge device having a cathode electrode, a grid electrode, an accelerating electrode and a collector electrode in the order named, said cathode electrode having radially extending leads, said grid electrode having supports and leads extending between but out of contact withsaidcathode leads, a cavityresonator coupled between the cathode leads andthe grid leads on the other side of the crossed over portions from said cathode and grid electrodes, said accelerator electrode being positioned adjacent said grid electrode, a capacity coupling between said accelerating electrode and said cathode electrode, and an inductive output resonator positioned between said accelerator electrode and said collector electrode.

5. An electron discharge device having an elongated envelope and containing in the order named a cathode electrode, control grid electrode, accelerating electrode and collector electrode, said cathode electrode being provided with a collar-like element coaxial with said cathode electrode, conducting means supporting said cathode electrode from said collar, conducting means extending through said envelope and supporting said collar, said grid electrode having supporting means extending through the supporting means for said cathode electrode and of said first resonator adjacent the cathode collar.

supporting means. I

6. An electron discharge device having an elongated envelope and containing in the order named a cathode electrode, grid electrode, accelerator electrode and collector electrode, said cathode electrode having a collar coaxial with said cathode electrode and conducting means extending between said collar and said cathode electrode and supporting said cathode electrode from said collar, said collar being provided with radially extending conducting means extending through and sealed to the wall of the envelope of said tube, conducting means supporting said grid electrode and extending through but out of contact with the supporting means for said cathode electrode and extending through and sealed to the wall of the envelope of said tube, and a coaxial line cavity resonator outside said envelope coupled between the conducting means supporting said grid electrode and the said radially extending conducting means, radially extending conducting means supporting said accelerator electrode extending through and sealed to the envelope of said tube, and a resonator having a pair of spaced collar-like elements providing a gap, surrounding said envelope, one of said collar-like elements being provided with means contacting the conducting supporting means for said accelerator electrode and having a flange capacity coupled to the coaxial line resonator to capacity couple said accelerator electrode and cathode electrode together.

7. An electron discharge device having a cathode electrode, grid electrode, accelerator electrode and collector electrode arranged in the order named, said cathode electrode comprising a collar and an emitting portion, and conducting means extending between said collar and said emitting portion and supporting said emitting portion from said collar, radially extending conducting means connected to said collar, and said grid electrode comprising a ring-shaped member supporting a foraminous material, and conducting and supporting leads connected to said ringshaped member and extending through but out of contact with the supporting means for said emitting portion of said cathode electrode, and a resonator outside said envelope having one side coupled to said leads and its other side connected to the radially extending conducting means connected to the cathode collar, and a resonator outside said envelope positioned between the accelerator electrode and the collector electrode and connected to said accelerator electrode, and means capacity coupling said accelerator electrode to said cathode electrode.

8. An electron discharge device having aligned cathode, grid and collector electrodes arranged in that order, said cathode electrode having radially extending supports and leads, said grid electrode having supports and leads extending between but out of contact with said cathode leads, a cavity resonator coupled between the cathode leads and the grid leads on the other side of the crossed-over portions from said cathode electrode and grid electrode and an inductive output cavity resonator positioned between said grid electrode and said collector electrode.

LEON S. NERGAAR-D.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,117,098 Linder May 10, 1938 2,167,201 Dallenbach July 25, 1939 2,169,896 Samuel Aug. 15, 1939 2,216,170 George Oct. 1, 1940 2,227,376 Hansen et a1. Dec. 31, 1940 2,284,751 Linder June 2, 1942 

